The Protein Kinase C βII Exon Confers mRNA Instability in the Presence of High Glucose Concentrations

Abstract Previous studies showed that short term exposure of cells to high glucose destabilized protein kinase C (PKC) βII mRNA, whereas PKCβI mRNA levels remained unaltered. Because PKCβ mRNAs share common sequences other than the PKCβII exon encoding a different carboxyl terminus, we examined PKCβII mRNA for a cis-acting region that could confer glucose-induced destabilization. A β-globin/growth hormone reporter con struct containing the PKCβII exon was transfected into human aorta and rat vascular smooth muscle cells (A10) to follow glucose-induced destabilization. Glucose (25 mm) exposure destabilized PKCβII chimeric mRNA but not control mRNA. Deletion analysis and electrophoretic mobility shift assays followed by UV cross-linking experiments demonstrated that a region introduced by inclusion of the βII exon was required to confer destabilization. Although a cis-acting element mapped to 38 nucleotides within the βII exon was necessary to bestow destabilization, it was not sufficient by itself to confer complete mRNA destabilization. Yet, in intact cells antisense oligonucleotides complementary to this region blocked glucose-induced destabilization. These results suggest that this region must function in context with other sequence elements created by exon inclusion involved in affecting mRNA stability. In summary, inclusion of an exon that encodes PKCβII mRNA introduces a cis-acting region that confers destabilization to the mRNA in response to glucose.